Abstract
Background: There have been previous reports of enhanced sympathoexcitation in autism spectrum disorder (ASD). However, there has been no formal investigation of autonomic dysfunction in ASD. Also, the joint hypermobile form of Ehlers-Danlos syndrome (hE-DS) that maybe overrepresented in ASD and orthostatic related autonomic dysfunction. This study examined the comorbidity of ASD, autonomic dysfunction and hE-DS in two UK autonomic national referral centers. Proven, documented and globally accepted clinical autonomic investigations were used to assess neuro-cardiovascular autonomic function in a cohort of ASD subjects and in age-matched healthy controls.Methods: Clinical data from 28 referrals with a confirmed diagnosis of ASD over a 10-year period were compared with 19 age-matched healthy controls. Autonomic function was determined using methods established in the centers previously described in detail.Results: 20/28 ASD had a diagnosed autonomic condition; 9 had the postural tachycardia syndrome (PoTS), 4 PoTS and vasovagal syncope (VVS), 3 experienced presyncope, 1 essential hyperhidrosis, 1 orthostatic hypotension, 1 VVS alone and 1 a combination of PoTS, VVS and essential hyperhidrosis. 16/20 ASD with autonomic dysfunction had hE-DS. In ASD, basal heart rate and responses to orthostatic tests of autonomic function were elevated, supporting previous findings of increased sympathoexcitation. However, sympathetic vasoconstriction was impaired in ASD.Conclusion: Intermittent neuro-cardiovascular autonomic dysfunction affecting heart rate and blood pressure was over-represented in ASD. There is a strong association with hE-DS. Autonomic dysfunction may further impair quality of life in ASD, particularly in those unable to adequately express their experience of autonomic symptoms.
Highlights
Homeostatic regulation is facilitated by the autonomic nervous system (ANS) and its ability to mediate activity of bodily organs especially the heart and blood vessels via peripheral efferent nerves
Despite the co-occurrence of hypermobile form of EhlersDanlos syndrome (hE-DS) in autism spectrum disorder (ASD) and forms of orthostatic intolerance, a detailed investigation into the presence of autonomic disorders in ASD has not yet been undertaken. Autonomic dysfunction in those with ASD may further impair morbidity and quality of life (QoL), and this study examined the potential comorbidity of ASD and clinical autonomic dysfunction, focusing on intermittent autonomic disorders, in two UK national referral centers for autonomic disorders that have worked in unison
Of the 28 ASD group, 3 were unable to complete the full test protocol due to anxiety, joint pain or apneic episodes but their data was analyzed until the cessation of testing
Summary
Homeostatic regulation is facilitated by the autonomic nervous system (ANS) and its ability to mediate activity of bodily organs especially the heart and blood vessels via peripheral efferent nerves. The literature investigating autonomic function in autism spectrum disorder (ASD), during behavioral studies, report a prevalence of enhanced sympathoexcitation (increased cardiovascular and sudomotor activity) (Althaus et al, 2004; Bal et al, 2010; Porges et al, 2013). In comparison to controls and on cardiovagal function, some studies have found vagally-mediated cardiac modulation to be increased in ASD (Toichi and Kamio, 2003), whilst others have found the opposite (Bal et al, 2010). The purpose of this study was to use clinical laboratory investigations to determine if there was autonomic dysfunction or an autonomic disorder in a cohort with ASD, in comparison with age-matched healthy controls. Proven, documented and globally accepted clinical autonomic investigations were used to assess neuro-cardiovascular autonomic function in a cohort of ASD subjects and in age-matched healthy controls
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